A corpobation op dblawabb



. ture near the boiling point,

Reiuued Apr. 4, 1933 WERNER IECKLEHBUBG, OI IOSCOW,

BIGNOB, 321mm ASSIGNMENTS,

UNION OI SOVIET SOOIALIBT BEPUBLIOS, AB- .IFO KBEBS 216mm 0010B GORPORATION, OI

NEWARK, imw messy, a concussion or nmwm monomer or mm moxmas llo Drawing. flrlglnal No. 1,758,828, dated! 18, 1980, lerlal Io.

338,818, fled I'Ih'ury 1, 1m,

and in Czechoslovakia lay i, 1888. Application for reluae fled April 1!, 1988. Serial No. 004,881.

This invention relates to a process for the production of titanium dioxide by the hydrolysis of titanium salt solutions.

When titanium salt solutions such as the sulfate or chloride are heated to a temperah drolysis occurs and a precipitate of Tio is formed. At the same time, the acidity of the mother liquor is increased on account of the formation of additional free acid.

Dilute solutions of hydrolyzable titanium salts such as the sulfate or chloride are more easily hydrolyzed than concentrated solutions, but at the same time the economical production of titanium dioxide by this process requires the use of fairly concentrated salt solutions since, otherwise, the free acid obtained as a byproduct is too dilute to permit recovery and reconcentration.

In previously developed hydrolysis rocesses various plans have been advanced for conducting the operation in concentrated solutions. For example, hydrolysis has been efl'ected by boiling the solutions at atmospheric pressure, in vacuo, and at elevated pressure. In other processes, hydrolysis has been accomplished by diluting a hot ver concentrated solution with water or wit mother liquor from previous hydrolyses.

Whenever titanium salt solutions are subjected to hydrolysis, a certain lag or induction period is observed between the commencement of the operation and the first visible precipitation, and it is believed that during this induction period, colloidal articles of TiO are formed in the solution; which particles serve as centers for the accumulation of additional hydrolyzed particles and result in the formation of aggregates which produce a visible precipitate. In view of this explanation of the hydrolysis reaction, one might expect that the addition of TiO produced by hydrolysis to a solution to be hydrolyzed would hasten the reaction. It has been found, however, that TiO -produced by the ordinary hydrolysis reaction, whether colloidal or not-does not produce the desired seeding action.

I have now discovered a process for preparing a special form of titaniferous material which, when added to a concentrated heated titanium salt solution such as the sulfate or the tetrachloride will produce a rapid and complete hydrolysis. One aspect of the invention deals with the production of this special material, hereinafter called seed suspension. Another aspect of the invention relates to the use of said suspensions in the hydrolysis process.

By neutralizing a titanium solution, such as is used for hydrol sis, with sodium hydroxide, using methy orange or bromphenol blue as an indicator, an aqueous mixture comprising a sodium salt solution and a suspension of titanium hydroxide is formed. If this mixture is maintained at an elevated temperature, in the neighborhood of 100 0., for a few minutes, some change in properties not well understood, occurs and the men tant material may be usedas a seed suspension for hydrolysis.

If a small amount of such a seed suspension is added to a hydrolyzable titanium solution, the mixture will appear turbid unless or until the temperature of the mixture is raised above 50-60 C. At about this temperature the turbidity disappears, the titanium hydroxide apparently dlssolving in the solution. If the titanium solution, thus seeded, is maintained at about 100-105 C. for three hours the titanium content is almost entirely precipitated as Tio the yield of this material being in excess of 95%. Under the same conditions, an unseeded solution yields no more than 35-70% of TiO,. As little as 1% of seed (based on the weight of seed TiO as compared to precipitated 150, is sufficient to produce the desired result. The seed suspension, once prepared, does not deteriorate even after months of standing.

The advantages of this method of hydrolysis over others known in the art are obvious. By means of this improvement, it is possible to completely hydrolyze concentrated titanium solutions without long hours of boiling (which invariably produces a relatively poor result), without treatment under pressure, and without diluting the solution to be treated with either water or mother liquor from a previous hydrolysis.

Now ha' orally described the inventioii, c iil ustrations of its use will be given. To conduct the hydrol sis it is first nry to prepare the see suspension. This is accomplished by combining hydroxide with (for example) a titanium sulfate solution to reduce the hydrogen-ion concentration to a point within the range p114 to pH4.5. Within this range, the titanium hydoxide is large- 1 preckiisitated to form a suspension w1 t al sulfate solution formed as a byproduct of the reaction.

When the requisite proportions of titanium sulfate solution and normal alkali h droxide solution have been determined, t e seed suspension is prepared by stirring the two materials together at a temperature of about 7 480 C. This mixture is then maintained at a temperature of about 80 C. for from fifteen to thirty minutes. At the end of this treatment the resultant seed suspension may be used for the hydrolysis 0 titanium sulfate solution or it may be set aside for future use. If the material is not to be used immediately, the temperature should be promptly reduced to below 60 C. at the end of the heat treatment. This may conveniently be accomplished by adding an equal volume of cold water. Thus treated, the seed suspension is converted to a stable form and may be stored for months without deterioration.

While a convenient method of producing the seed suspension has been described, it should be understood that merely illustrative and is by no means limiting. A suitable material may be prepared by other methods, the only requisite items being that the titanium sulfate solution be reduced to the propler hydrogen-ion concentration and that t e resultant material be heat-treated at 80100 C. for fifteen to thirty minutes. In place of an alkali hydroxide such as the hydroxide of sodium, potassium, or ammonium, the alkaline carbonates may be employed to reduce the hydrogen-ion concentration of the titanium sulfate solution to the roper point.

vyhen the seed sus ension is introduced into cold titanium sul ate solution, no reaction of any sort is apparent. If it is introduced into a hot solution, the suspended titanium hydroxide apparently dissolves and the mixture is not turbid. If the seeded titanium sulfate solution is maintained at 100-105 C. (this being slightly below the boiling point) for about three hours, the titanium is completely hydrolyzed to form T the yield being in excess of 95%, and sometimes as high as 98%. The TiO thus produced ma be removed by filtration and the mother liquor may be concentrated and used again for the treatment of ore, or for other purposes.

this example is The amount of seed on used to promote hydrolysis may be varied as desired. As little as 1% of TiO, in the seed solution as compared to the T10, in the titanium sulfate solution 'ves satisfactory results. More may be u but the addition of a greater quantity dilutes the mother liquor which it is desired to reconcentrate. In practice, the titanium hydroxide in the seed solution may be allowed to settle and some of the clear li uor (containing soluble sulfates) may be e'canted ofi. The more concentrated seed solution may then be employed in proportionate quantity.

As illustrative of the results obtained by my improved method of hydrolysis, the following table of data obtained with certain variations of the process is submitted. In all of the cases mentioned, 400 cc. of titanium sulfate solution were mixed with cc. of seed suspension and the mixture was maintained at a temperature near the boiling point for three hours. Y

' care Titanium sullam sol. grams Seed :1 Hydrolysis yield 0! T101 per liter 'I'iO: mso. Age Alkali Eff 1 m. 2 hrs. a m.

Hn. Percent Per cent Per sent an as 24 NaOH 2? am an 05.2 no so NaOH in can us 00.1 no mo 0 NaOH 4.5 an sea 213 $88 0 KO 2. 8 95.0

502 72 Ron I. 8 00. 8 185 465 0 K03 3. 2 9L 0 an 440 o NH40H 4.3 ess can an no is Nmon 4.4 01.2 95.9

As prevlousl indicated, the advantages to be gained by t e improved hydrolysis process depend in part on the economic improvement afiorded by operating with concentrated solutions. However, the invention is equally applicable and operative in the case of dilute solutions.

While I prefer to use seed suspensions at a hydrogen-ion concentration of about 4-4.5 as previously specified, my invention is capable of a wider use, as is shown in the above tabulation. In working with suspensions of greater acidity than pH 4e. g. 2.5-4.0 as shown in the tabulation, great must be exercised to cool the seed suspension to C. immediately after the formation reaction and the period of heating should be shorti. e. about fifteen minutes. On the other hand, seed suspensions may be prepared at a hydro en-ion concentratlon of pH 4.5-6.0 by slig tly increasing the duration and temperature of heating.

From the character of the seed, which is actually a suspension of titanium hydroxide produced at a point near neutrality, and from the behavior of the seed suspension when added to the solution to behydrolyzed, it appears probable that the titanium bydroxide is not actually dissolved on heatin but is converted to some colloidal form whic promotes the hydrolysis of titanium sulfate solutions. However, the result attained differs from other hydrolysis processes which are apparently promoted by the formation of colloidal particles pr1or to actual precipitation in at least two 1mportant respects:

(a) The quantity is much smaller;

(b) The desired result is attained without diluting the solution.

While the explanation given appears reasonable, any and all theories andexplanations of the process are disclaimed and for a matter of convenience the expressions titanium hydroxide and titanium oxygen compound are used herein to designate the precipitate obtained by reducing the acidity of a titanium salt solution, at any stage of its pro aration and without reference to its exact c emical composition.

I claim:

1. A composition comprising titanium hydroxide in aqueous suspension at a hydrogen ion concentration of about pH 2.5-6.0.

2. In a process of preparing a seed suspension for use in the hydrolysis of a titanium salt solution, the steps of mixing together a neutralizing agent and a titanium salt solution until precipitation of a titanium oxygen compound is efl'ected and heating the precipitate to about 80 to 100 C. for 15 to 30 minutes.

3. In a process of preparing a seed suspension for use in the hydrolysis of a titanium salt solution, the steps of mixing caustic soda and a titanium sulfate solution until precipitation is eifected and heating the mixture to about 80 to 100 C. for 15 to 30 minutes.

4. The process of preparing a seed suspension for use in the hydrolysis of a titanium salt solution, which comprises mixing together sufficient neutralizing agent and a titanium sulfate solution to precip1tate a titanium oxygen compound and to reduce the acidity of the mixture to a hydrogen-ion concentration of pH 2.5-6.0 and heating the precipitate to about 80 to 100 C. for 15 to 30 minutes.

5. A process for preparing a seed suspension which comprises reducing at elevated temperature the acidity of a titanium salt solution to a hydrogen-ion concentration of pH 2.5-6.0 and cooling the mixture to below 60 C.

6. The process of producing a seed for use in the hydrolysis of a titanium salt solution which comprises precipitating a titanium oxygen compound by reducing the acidity of a titanium salt solution and heating the precipitate formed under conditions such that the precipitate when added in small amount of promotion material to a hydrolyzable titanium salt solution followed-by three hours heating to the boiling point roduces a hydrolysis yield in excess of 0, said conditions having been established by recipitating a titanium oxygen compound rom a similar solution at various degrees of acidity, at various temperatures and maintaining said precipitate for various lengths of time at said temperatures and determining in each instance the effect of such precipitated compounds upon the hydrolysis yield of a titanium salt solution.

7. In a process for the production of titanium dioxide the steps which comprise adding to a titanium salt solution a precipitated seed prepared separatel and heatm said mixture to produce hydro ysis, said see comprising a titanium oxygen compound which dissolves on heating in said titanium salt solution.

8. In a process for the production of titanium dioxide the steps which comprise adding to a titanium salt solution a suspension of a precipitated seed prepared separately and heating said mixture to produce hydrolysis, said seed comprising a titanium oxygen compound which dissolves on heating in said titanium salt solution.

9. In a process for the production of titanium dioxide the steps which comprise adding to a titanium sulfate solution a suspension of a precipitated seed prepared separately and heating said mixture to produce hydrolysis, said seed comprising a titanium oxygen compound which dissolves on heating in said titanium sulfate solution.

10. In a process for the production of titanium dioxide, the steps comprising adding a titanium oxygen com ound to a precipitated titanium salt solution and heating said mixture to effect hydrolysis, said titanium oxygen compound being at least partly soluble on heating in said titanium salt solution and being further characterized by having been prepared by a process which includes as one 0 its steps precipitation by the reduction of the acidity of a titanium salt solution by mixing it with a neutralizing agent.

11. In a process for the production of titanium dioxide, the steps comprising adding a precipitated titanium oxygen compound to a titanium sulfate solution and heating said mixture to eifect hydrolysis, said titanium oxygen compound being at least partly soluble on heating in said titanium sulfate solution and being further characterized by having been prepared by a process which includes as one of its steps precipitation by ,the reduction of the acidity of a titanium sulfate solution by mixing it with a neutralizing agent.

12. In a process for the production of titanium dioxide. the steps comprising adding a precipitated titanium oxygen compound to a salt solution and heating said mixture to effect hydrolysis, said titanium oxygen compound bein at least partly soluble on heating in sai titanium salt solution, and being further characterized by having been prepared by a (process which includes as one of its steps igesting a precipitated titanium oxygen compound in a slightly acid to neutral reacting, aqueous medium at an elevated temperature for an appreciable length of time, but not long enough to render it completely insoluble in said titanium salt solution.

13. In a process for the production of' titanium dioxide, the steps comprising adding a precipitated titanium oxygen compound to a titanlum sulfate solution and heating said mixture to efiect hydrolysis said titanium oxygen compound being at feast partly soluble on heating in said titanium sulfate solotion, and being further characterized by having been prepared by a process which includes as one of its steps digesting a precipitated titanium oxygen compound in a slightly acidto neutral reacting aqueous medium at an elevated temperature for an appreciable length of time, but not long enough to render it com letely insoluble in said titanium sulfate so ution.

14. In a process for the production of titanium dioxide, the steps comprising addmg a precipitated titanium oxygen compound to a titanium salt solution and heating said mixture to efiect h drolysis, said titanium 'oxygen compound eing at least partly soluble on heating in said titanium salt solution and being further characterized by hav ing been produced by maintaining for a short time at an elevated temperature the precipitate obtained by reducing the acidity of a titanium salt solution when mixing it with a neutralizing agent.

15. In a process for the production of titanium dioxide, the steps comprising adding a precipitated titanium oxygen compound to a titanium sulfate solution and heating said mixture to effect hydrolysis, said titanium oxygen compound being at least partly soluble on heating in said titanium sulfate solution and being further characterized by having been produced by maintaining for a short time at an elevated temperature the precipitate obtained by reducing the acidity of a titanium sulfate solutionwhen mixing it with a neutralizing cut.

16. A process for t e production of titanium dioxide which comprises addinga mixture containing titanium hydroxide in aqueous suspension containing sodium sulfate to a solution of titanium sulfate, and maintaining the mixture at a temperature near the boilin point.

17. in a process of hydrolyzing a titanium salt, the steps of reducing the acidity of a titanium salt solution thereby precipitating a titanium oxygen com and therefrom, mixing said prec1pitate with a titanium salt solution containing substantially more titanium than that added, and heating the mixture to effect hydrolysis.

18. In a process of hydrolyzing titanium sulfate, the steps of reducing the acidity of a titanium sulfate solution by mixing said solution with a neutralizing agent, thereby precipitating a titanium oxygen compound therefrom, mixing said precipitate with a titanium sulfate solution containing more titanium than that added, and heating said mixture to effect hydrolysis.

19. In a process of hydrolyzing titanium sulfate, the steps of reducing the acidity of a. titanium sulfate solution to a pH from 2.5-6.0 by mixing it with a neutralizing agent, whereby a titanium oxygen compoun is precipitated, heating said precipitate to about 80 to 100 C. for from 15 to 30 minutes, mixing said titanium oxygen compound with a titanium sulfate solution containing more titanium than that added, and heating the mixture to effect hydrolysis.

20. A process for the production of titanium dioxide which comprises mixin about one part of titanium dioxide in the orm of an aqueous suspension of titanium dioxide in a solution having a hydrogen-ion concentration of pH 2.5-6.0 with one hundred parts of titanium dioxide in the form of a sulfate solution, and maintaining the mixture at a temperature near the boiling point.

21. A process for the production of titanium dioxide which comprises adding about one part of titanium dioxide in the form of an a ueous suspension of titanium dioxide in a 5111 ate solution having a hydrogen-ion concentration of pH 2.5-6.0 to one hundred parts of titanium dioxide in the form of a sulfate solution containing about 180 grams per liter of TiO and 400 grams per liter of titratable acid, and maintaining the mixture at a temperature near the boiling point.

22. A process for the hydrolysis of a titanium sulfate solution which comprises addin sufficient alkali to a small portion of said so ution to reduce the acidity to a pH 2.5-6.0 and to precipitate titanium hydroxide therein, heating said mixture to about 80 C. for 15 to 30 minutes, mixing said mixture with the rest of the titanium sulfate solution, and maintainin the mixture at a temperature near the boiling point.

23. A process for the production of titanium dioxide which comprises mixing an aqueous suspension containing titanium hydroxide at a hydrogen-ion concentration of about pH 2.5-4.5 with a solution of titanium sulfate and maintaining the mixture at a temperature near the boiling point.

24. A process for the production of titanium dioxidewhichcomprisesmixinganaqueous suspension containing titanium hydroxide at a hydrogen-ion concentration of about H 2.5-6.0 with a solution of titanium sulate at a temperature below 50 (3., heatin the solution to near the boiling point an maintaining it at this temperature.

25. A recipitated titanium oxygen compound w ich is soluble at an elevated temperature in a titanium sulfate solution containing 200 grams TiO, and 440 H 50 free and combined with Ti per liter, which compound, when added to a titanium sulfate solution, accelerates at elevated temperature the hydrolysis of said titanium sulfate.

26. A precipitated titanium oxygen compound w ich is soluble at an elevated temperature in a titanium sulfate solution containing 200 grams TiO and 440 ams H,SO, free and combined with Ti per liter, which compound, when added to a titanium sulfate solution, accelerates at elevated temperature the h drol sis of said titanium sulfate and whic is urther characterized by having been produced by reducing the acidity of a titanium salt solution by the addition thereto of a neutralizing agent.

In witness whereof, I afiix m s1 ature.

WERNER MECKLLNB RG.

CERTIFICATE OF CORRECTION.

Reissue No. 18, 790. April 4, I933.

WERNER MECKLENBURG.

[t is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, lines 104 and 105, claim 10, strike out the word "precipitated" and insert the same before "titanium" in line 104, of same claim; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 23rd day of May, A. D. 1933.

M. J. Moore.

(Seal) Acting Commissioner of Patents. 

